Duplex Stainless Steels

Summary Tables

Duplex Stainless Steels

Duplex stainless steels have a ‘duplex’ two-phase micro-structure consisting of both austenitic and ferritic grains that gives them a combination of attractive properties. Duplex alloys were developed around a 22% Chromium addition level, which largely defines them from subsequent super duplex alloys which were developed around a 25% Chromium addition level for higher corrosion resistance still.

In general, they are twice as strong as either austenitic or ferritic stainless steels. They achieve good toughness and ductility, somewhere between the two. Their corrosion resistance is also very good, assuming comparable levels of Chromium, Molybdenum and Nitrogen in selected compositions. One important advantage over austenitic stainless steels is their resistance to stress corrosion cracking. Yet they are significantly more cost effective, and less prone to price variability, due to their lower nickel content.

Summary Tables

Summary Tables

AlloyCommon NameRelated SpecificationsTensile StrengthProof TestElongation
BritishEuropeanUnited StatesN/mm2 (ksi)N/mm2 (ksi)(%)
Sanmac 2205Duplex 2205318S131.4462
X2CrNiMoN22.5.3
AFNOR Z2CND22.05Az
Sandvik SAF2205
Norsok MDS D47
ASTM A276 S31803/S2205
ASTM A182 F51 / F60
22 Cr
655 (95)450 (65)25
Sanmac 2205 (Hollow Bar)UNS S31803/S32205UNS S32205
UNS S31803
EN 1.4462
X2 CrNiMoN 22-5-3
ASTM A790
NACE MR 1075 / ISO 15156
ASME Case 2067-2
22 Cr
680 (99)450 (65)25
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